Aqueous absorption systems

Recovery and Purification. AH processes for the recovery and refining of maleic anhydride must deal with the efficient separation of maleic anhydride from the large amount of water produced in the reaction process. Recovery systems can be separated into two general categories aqueous- and nonaqueous-based absorption systems. Solvent-based systems have a higher recovery of maleic anhydride and are more energy efficient than water-based systems. 

In a typical batch operation, carbon disulfide is added to four molar equivalents of 25—30 wt % aqueous ammonia in a stirred vessel, which is kept closed for the first one to two hours. The reaction is moderately exothermic and requires cooling. After two to three hours, when substantially all of the disulfide has reacted, the reaction mixture is heated to decompose dithiocarbamate and trithiocarbonate and vented to an absorption system to collect ammonia, hydrogen sulfide, and any unreacted carbon disulfide. 

The ammonia-water absorption system was extensively used until the fifties when the LiBr-water combination became popular. Figure 11-103 shows a simplified ammonia-water absorption cycle. The refrigerant is ammonia, and the absorbent is dilute aqueous solution of ammonia. Ammonia-water systems differ from water-lithium bromide equipment to accommodate major differences Water (here absorbent) is also volatile, so the regeneration of weak water solution to strong water solution is a fractional distillation. Different refrigerant (ammonia) causes different, much higher pressures about 1100-2100 kPa absolute in condenser. 

The primary reason for studying aqueous plutonium photochemistry has been the scientific value. No other aqueous metal system has such a wide range of chemistry four oxidation states can co-exist (III, IV, V, and VI), and the Pu(IV) state can form polymer material. Cation charges on these species range from 1 to 4, and there are molecular as well as metallic ions. A wide variety of anion and chelating complex chemistry applies to the respective oxidation states. Finally, all of this aqueous plutonium chemistry could be affected by the absorption of light, and perhaps new plutonium species could be discovered by photon excitation. 

The UV absorption of the aqueous vesicular systems, which provides information on the relative concentration of lipids in aqueous system, also proved the enhanced stability of the polymerized vesicles. The absorptions at 238 nm of the unpolymerized vesicles showed a sharp decrease, as seen in Figure 5, as a result of the precipitation of the lipid in the system. However, the absorptions at the same wavelength of the polymerized system showed a relatively steady trend that meant the polymerized lipid had a longer suspension life in the aqueous system. 

Absorption - Intraocular penetration occurs after topical instillation. Decreased corneal integrity or stromal or uveal inflammation may enhance the penetration into the aqueous humor. Systemic absorption following therapeutic dosing appears negligible. 

In the presence of water, polymers reveal a greater sensitivity to radiation. This increase has been shown to be caused by the indirect effect of radiation—i.e., the radiolytic products of water react with and form new radicals in the dissolved polymer. This indirect effect is also present in aqueous biological systems. The usual ESR techniques do not enable such radicals to be readily revealed because of the high absorption of water, but other techniques using radical scavengers reveal their presence. 

Extremely inhomogeneous conditions are found in oxidative degradation processes induced by vacuum ultraviolet (VUV) irradiation of aqueous reaction systems. In fact, the absorption cross section of water for an almost monochromatic excitation at 172 nm (Xe excimer lamp, vide infra) being very... 

There have been very few studies on the kinetics of micellization in block copolymer solutions. Micellization in aqueous surfactant systems close to equilibrium occurs on a time-scale far below one second. Experimental results obtained by fast reaction techniques, such as temperature jumps or pressure jumps or steady-state methods such as ultrasonic absorption, NMR and ESR, show that at least... 

McCann N, Maeder M, Attalla M (2008) Simulation of enthalpy and capacity of C02 absorption by aqueous amine systems. Ind Eng Chem Res 47(6) 2002-2009... 

Absorption Abatement or extended absorption refers to modifications that involve the addition of increased absorption capacity or optimization of the existing absorption system to oxidize and react the nitrogen oxides with water to form acid.. Tail gases are passed through an absorber containing either water or an aqueous solution of ammonia, urea or sodium hydroxide. When water is used as the absorbent, the resultant weak acid is recycled. This increases nitric acid yields by 1% to 3%. When other absorbents are used, the recovered NOx is typically consumed in the production of nitrogen solutions for fertilizer use. If sodium hydroxide is the absorbent, pure sodium nitrite and sodium nitrate may be recovered91,104. 

The Shell Sulfinol Process is used for removal of acidic constituents such as H2S, CO2, COS, etc. from a gas stream. Improved performance over other processes is due to the use of an organic solvent, Sulfolane (tetrahydrothiophene dioxide), mixed with an aqueous alkanolamine. Relative proportions of Sulfolane, alkanolamine, and water, as well as the operating conditions, are tailored for each specific application. Simultaneous physical and chemical absorption under feed gas conditions is provided by this Sulfinol solvent. Regeneration is accomplished by release of the acidic constituents at near atmospheric pressure and a somewhat elevated temperature. The flow scheme (Figure 4) is very similar to that of an aqueous alkanolamine system since it involves only absorption, regeneration and heat exchange under typical alkanolamine treater conditions. 

The recovery area uses a patented organic solvent to remove the maleic anhydride from the reactor effluent gas. A conventional absorption (2)/stripping (3) scheme operates on a continuous basis. Crude maleic anhydride is distilled to separate light (4) and heavy (5) impurities. A slipstream of recycle solvent is treated to eliminate any heavy byproducts that may be formed. The continuous non-aqueous product recovery system results in superior product quality and savings in steam consumption. Relative to an aqueous recovery system, it reduces investment, product degradation loss (and byproduct formation) and wastewater. 

DA Paterson, RA Conradi, AR Hilgers, TJ Vidmar, PS Burton. A non-aqueous partitioning system for predicting the oral absorption potential of peptides. Quant Struct-Act Relat 13 4—10, 1994. 

Investigating the pulse radiolysis of aqueous nitrate system by kinetic absorption spectroscopy led to the discovery (8, 9) of the characteristic absorption spectrum of the NOa radical in neutral solutions—... 

Alkali is also added to the water fraction in an amount sufficient to react with all ammonium compounds and with phenol. pon fractional distilla tion, ammonia is first expelled and then recovered in a suitable absorption system. An aniline-water fraction is next distilled, from which an aniline layer separates out on cooling. The supernatant aqueous portion con-... 

Curcumin was readily solubilised in aqueous surfaciam systems in which the surfactant concent nil ion was above the critical micelle concentration (cmc). In each case the electronic absorption spectrum was independent of surfactant concentration above the cmc. 

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